The present invention relates to internal combustion engines. In an internal combustion engine, the basic functionality includes: (1) the intake of a fuel-air mixture into a combustion chamber; (2) the compression of the fuel-air mixture; (3) the ignition of the fuel-air mixture; and (4) the expansion of the ignited mixture and exhausting of the combustion gases. The resultant release of energy in the form of expanding gas is used to power various mechanical devices, including vehicles.
A reciprocating internal combustion engine is perhaps the most common form of internal combustion engine. In a reciprocating internal combustion engine, the reciprocating motion of a piston in a cylinder results in the compression of the fuel-air mixture and the expansion of combustion gases. The energy is transformed from linear motion into rotational motion through connection of the piston to a crankshaft.
Most modern vehicle engines currently use a piston-cylinder arrangement in what is referred to as a four-stroke combustion cycle, comprised of (1) an intake stroke, (2) a compression stroke, (3) a combustion stroke, and (4) an exhaust stroke. In a four-stroke combustion cycle using a typical piston-cylinder arrangement, the piston starts at the top of the combustion chamber (i.e., the cylinder), and an intake valve opens. The piston moves downwardly within the cylinder, and the fuel-air mixture is drawn into the cylinder through the intake valve, completing the intake stroke. The piston then moves back upwardly to compress the fuel-air mixture until reaching the top of the stroke, completing the compression stroke. When the piston reaches the top of the stroke, the spark plug ignites the compressed fuel-air mixture, resulting in a controlled explosion that drives the piston downwardly, completing the combustion stroke. Finally, once the piston reaches the bottom of its stroke, an exhaust valve opens, and combustion gases are forced out of the cylinder by the upward movement of the piston back to the top of its stroke, completing the exhaust stroke and readying the piston for a subsequent combustion cycle.
Although common in vehicles, a reciprocating internal combustion engine using a four-stroke combustion cycle does have some disadvantages. As a result, other engines have been developed that use the same basic combustion principles with some variation. For example, in an internal combustion engine using a two-stroke combustion cycle, the intake and exhaust valves are eliminated. Instead, intake and exhaust ports are located on opposite sides of the cylinder. After each expansion stroke, combustion gases under pressure exit the cylinder through the exhaust port, and a fuel-air mixture is drawn in through the intake port. Although there is only one expansion cycle per crankshaft revolution, a two-cycle engine is must less efficient than a four-cycle engine.
Another reciprocating internal combustion engine is a diesel engine, which can have a four-stroke or a two-stroke combustion cycle. Unlike the above-described engines, however, a diesel engine draws in and compresses only air in the cylinder. This air is compressed by the piston to more than 450 psi, resulting in an air temperature of about 900-1100° F. At the bottom of the compression stroke, diesel fuel is injected into the cylinder, and the temperature of the air within the cylinder is sufficient to cause ignition of the fuel-air mixture without the need for a spark plug.
In any event, a reciprocating internal combustion engine has its disadvantages. The piston has a significant mass and thus inertia, which can cause vibration during motion and limits the maximum rotational speed of the crank shaft. Furthermore, such engines have relatively low mechanical and fuel efficiencies.
As a result of such disadvantages, some attempts have been made to propose alternate combustion engine designs. Perhaps the most well-known and commercially successful of these alternate designs is the Wankel or rotary piston engine. The Wankel engine has a quasi-triangular rotating piston that moves along an eccentric path to rotate the crankshaft. Rather than using inlet and exhaust valves, the edges of the rotating piston open and close ports in the wall of the combustion chamber. In other words, intake and exhaust timing are controlled solely by the motion of the rotor.
As the piston of the Wankel engine rotates, seals mounted at its three corners continuously sweep along the wall of the combustion chamber. The enclosed volumes formed between the piston and the wall increase and decrease through each revolution of the piston. A fuel-air mixture is drawn into an enclosed volume, compressed by the rotation of the piston that decreases the enclosed volume, and then ignited with the combustion gases being accommodated by and expelled through the expansion of the enclosed volume. In short, a complete four-stroke combustion cycle is achieved, but since there is no reciprocating motion, higher rotational speeds are possible.
The most pronounced disadvantage of a Wankel or rotary piston engine is the difficulty in adequately sealing the enclosed spaces between the piston and the wall of the combustion chamber that increase and decrease through each revolution of the piston. If these enclosed spaces are allowed to communicate with another, the engine cannot properly function.
Since development of the Wankel engine, some attempts have been made to address such shortcomings of a Wankel or rotary piston engine. For example, U.S. Pat. No. 5,415,141 describes and claims an engine that has a central rotor and a plurality of radially sliding vanes. The vanes rotate clockwise with the rotor to form enclosed volumes between the vanes, the side walls of the combustion chamber, and the rotor. These enclosed volumes decrease and increase in volume throughout the combustion cycle, with the fuel-air mixture being drawn into an enclosed volume, compressed by the rotation of the rotor and associated vane, and then ignited with the combustion gases being accommodated by and expelled through the expansion of the enclosed volume. Nevertheless, as with a Wankel engine, such a design still suffers from the problem of adequate sealing of the enclosed volumes from one another. Furthermore, the drag of the vanes along the wall of the combustion chamber reduces power and fuel efficiency.
As another alternative, U.S. Pat. No. 6,796,285 describes and claims an internal combustion engine that has a torque wheel mounted for rotation within the central cavity defined by a housing and driving a crankshaft. The torque wheel includes a plurality of separate arms in a spaced arrangement about the center of the torque wheel, thereby defining corresponding volumes between the respective arms. Positioned within these volumes are substantially identical combustion gates. As the torque wheel rotates, the combustion gates are moved through an elliptical path. Air is drawn into the central cavity of the housing, and fuel is introduced into the central cavity of the housing to create a fuel/air mixture in one of the volumes between the respective arms of said torque wheel and adjacent one of the combustion gates. This fuel/air mixture is then compressed during the continuing rotation of the torque wheel by the pivoting and outward movement of the combustion gate. The fuel/air mixture is then ignited, causing a rapid expansion of combustion gases and imparting a torque that causes continued rotation of the torque wheel. The combustion gate then pivots and moves inwardly toward the center of the torque wheel, allowing the combustion gases to expand, and then pivots and move outwardly again, forcing the combustion gases through an exhaust outlet.
Nevertheless, there remains a need for a durable, fuel-efficient internal combustion engine that can rotate faster than common gas-powered engines, while maintaining a constant rotational speed with a high power output to weight ratio.